So looming at AOC display website, it appears you can "setup" g-sync to be enabled...

Main thing, is that monitor plugged into a display port or one of the other types...

Is it set as the "primary" monitor?

You could disable all the g-sync for that monitor as a test. So on the g-sync tab and also in the monitor technology option of the 3d settings, all in nvidia driver....

Be sure to remove moi from the windows display control. Actually, i believe windows should have notified you that nvidia already had control... (but i could be wrong)